1. Field of the Invention
This invention relates to a method for filling liquid into a liquid container and also to an apparatus adapted to use such a method. More particularly, the present invention relates to a liquid filling method and a liquid filling apparatus for filling liquid into an ejection type liquid container adapted to contain liquid such as ink to be used in a liquid ejector.
2. Related Background Art
A liquid ejector (ink-jet apparatus) comprises a liquid ejection head for ejecting liquid such as ink and recording images such as characters and graphics and a liquid tank operating as liquid container for storing liquid such as ink to be fed to the liquid ejection head. Normally, the liquid tank has a structure adapted to be removably fitted to the liquid ejector so that it may be replaceable at any time. When a liquid tank that can be separated from the liquid ejection head is used and all the liquid in the liquid tank is consumed to make the tank empty so that the liquid ejector can no longer operate for recording images, the liquid tank is replaced by a new one filled with liquid so that the image recording operation can be resumed. On the other hand, in the case of a liquid ejector comprising a liquid tank and a liquid ejection head that are formed integrally relative to each other, the liquid ejection head needs to be replaced by new one when all the liquid in the liquid tank is consumed, regardless of the service life of the liquid ejection head. Therefore, the use of a liquid tank that is separable from the liquid ejection head is advantageous in terms of running cost if compared with a liquid tank of the integral type. Additionally, precious resources will be saved to a great advantage of environment protection if the emptied liquid tank is filled with liquid again for reuse.
Particularly, the use of separate type liquid tanks is desired for so-called mobile type printers that are compact and portable because such printers require the use of a compact liquid tank whose size and liquid containing capacity are made very small, reflecting the small size of the printer main body, and the liquid contained in the liquid tank can be used up quickly if compared with a stationary type printer that may be used on the top of a desk so that the liquid tank needs to be refilled frequently.
Various methods and devices have been proposed for refilling liquid into such a liquid tank. For instance, there are known methods with which liquid is filled into a liquid tank under pressure through an air inlet port or a refilling port bored through the wall of the tank. Refill kits to be used for manual refilling operations are also known and commercially available. With other known methods, the inner pressure of a liquid tank is reduced so that liquid may be filled into it conveniently. Such methods are popularly being used for filling liquid into mint liquid tanks.
However, methods for manually refilling a liquid tank that may contain residual liquid to some extent are accompanied by the following problems. Firstly, the effect of manual refilling operation is heavily dependent on the skill of the operator and the liquid tank may not be sufficiently refilled. More specifically, the operator is required to manually refill the liquid tank while applying pressure to the liquid to be filled into the liquid tank. As a matter of fact, the operator more often than not applies excessive pressure to the liquid. Then, the ink supply rate exceeds the rate at which liquid permeates the absorbent member in the liquid tank. The net result is that liquid is not filled into the inside of the liquid tank properly but overflows from the tank. Secondly, the operator is totally occupied by the liquid refilling operation and can not do any other operation because pressure needs to be applied in a well controlled manner as a function of the amount of liquid currently existent in the liquid tank. The refilling operation normally takes a long time. Again, the time required for the refilling operation can vary depending on the skill of the operator.
Automatic refilling devices have also been proposed in order to bypass the above problems and other problems of manual refilling operation. However, known automatic refilling devices have a complicated structure mainly because the pressure applied to the liquid to be filled into the liquid tank and the rate at which liquid is fed into the tank need to be controlled by sensing the internal condition of the liquid tank.
Some methods for refilling liquid into a liquid tank under pressure are designed to utilizes a refilling port. However, the liquid flow path of a liquid tank is formed in such a way that all the liquid contained in the liquid tank eventually comes to the liquid outlet port of the tank. In other words, the provision of a refilling port means that the liquid tank has a liquid flow path in the inside that is totally unrelated to the proper use of the liquid tank. Such an additional flow path can bias the liquid in the liquid tank and interfere with a smooth movement of liquid toward the liquid outlet port. Then, the liquid tank will operate unsatisfactorily.
On the other hand, known methods for refilling a liquid tank with liquid while reducing the internal pressure of the tank are mostly designed to fill liquid into mint liquid tanks. If such methods are applied to a liquid refilling operation, the refilling operation needs to be controlled as a function of the amount of residual liquid. Then, the refilling device to be used with such a method needs to be provided with means for detecting the amount of residual liquid and means for changing the extent of pressure reduction as a function of the amount of residual liquid to make the device very complicated one.
In view of the above identified problems of the prior art, it is therefore the object of the present invention to provide a liquid filling method and a liquid filling apparatus that can accurately refill liquid into a liquid container to be used with a liquid ejector regardless of the amount of liquid remaining in the container without requiring any complex control operation and other refilling arrangement.
In an aspect of the invention, the above object is achieved by providing a liquid filling method for filling liquid into a liquid container of the type having a porous liquid absorbent member arranged in the inside and adapted to hold liquid under negative pressure generated in the inside and communicating to a liquid ejection head so as to supply liquid from the inside to the liquid ejection head by way of a liquid outlet port, the method comprising:
a step of drawing out liquid remaining in the liquid container by way of the liquid outlet port;
a step of reducing the inner pressure of the evacuated liquid container by way of the liquid outlet port; and
a step of filling liquid from the inside of a liquid supply tank into the liquid container by way of the liquid outlet port.
Preferably, with the liquid filling method for filling liquid into a liquid container according to the invention, the liquid drawn out from the liquid container is fed back into the liquid supply tank.
Preferably, when drawing out the liquid remaining in the liquid container with the liquid filling method for filling liquid into a liquid container according to the invention, the time to be used for the step of drawing out the liquid remaining in the liquid container is determined on the basis of the relationship between the maximum liquid containing capacity of the liquid container and the means to be used for drawing out liquid and the liquid remaining in the liquid container is drawn out in a determined constant operation time regardless of the amount of liquid remaining in the liquid container. Preferably, when reducing the internal pressure of the liquid container with the liquid filling method for filling liquid into a liquid container according to the invention, the time to be used for the step of reducing the internal pressure of the liquid container is determined on the basis of the relationship between the maximum volume of gas containable in the inside of the totally evacuated liquid container and the means to be used for reducing the internal pressure of the liquid container and the internal pressure of the liquid container is reduced in a predetermined constant operation time.
In another aspect of the present invention, there is provided a liquid filling apparatus for filling liquid into a liquid container communicating to a liquid ejection head so as to supply liquid from the inside to the liquid ejection head by way of a liquid outlet port, said apparatus comprising:
a liquid drawing out means for drawing out the liquid remaining in the liquid container by way of the liquid outlet port;
a pressure reducing means for reducing the inner pressure of the evacuated liquid container by way of the liquid outlet port;
a liquid supply tank for storing liquid to fill the liquid container; and
a filling means for filling liquid from the inside of the liquid supply tank into the liquid container by way of the liquid outlet port.
Preferably, a liquid filling apparatus according to the invention further comprises a liquid feeding back means for feeding the liquid drawn out from the liquid container by the liquid drawing out means back into the liquid supply tank.
Preferably, a liquid filling apparatus according to the invention further comprises a collection tank for temporarily holding the liquid drawn out from the liquid container by the liquid drawing out means. Preferably, the capacity of the collection tank is substantially equal to the capacity of a liquid container that is largest among liquid containers expected to be refilled with liquid by the liquid filling apparatus. Preferably, the bottom surface of the collection tank is located above the liquid supply tank.
Preferably, in a liquid filling apparatus according to the invention, the liquid drawing out means is provided with a suction pump or piston cylinder mechanism and the drive time of the suction pump or piston cylinder mechanism is determined on the basis of the relationship between the performance of the suction pump or piston cylinder mechanism and the maximum liquid containing capacity of the liquid container so as to drive the suction pump or piston cylinder mechanism and draw out the liquid remaining in the liquid container for a determined constant operation time regardless of the amount of liquid remaining in the liquid container. Preferably, in a liquid filling apparatus according to the invention, the pressure reducing means is provided with a suction pump or piston cylinder mechanism and the drive time of the pressure reducing means is determined on the basis of the relationship between the performance of the suction pump or piston cylinder mechanism and the maximum volume of gas containable in the inside of the totally evacuated liquid container so as to drive the suction pump or piston cylinder mechanism and reduce the internal pressure of the liquid container for a determined constant operation time. Preferably, the liquid drawing out means and the pressure reducing means are commonly provided with a suction pump or piston cylinder mechanism.
Thus, according to the invention, with a liquid container of the type having a porous liquid absorbent member arranged in the inside and adapted to hold liquid under negative pressure generated in the inside and communicating to a liquid ejection head so as to supply liquid from the inside to the liquid ejection head by way of a liquid outlet port, the liquid remaining in the liquid container is drawn out by way of the liquid outlet port, the inner pressure of the liquid container is reduced by way of the liquid outlet port and liquid is refilled from the inside of a liquid supply tank into the liquid container by way of the liquid outlet port. With this arrangement, it is now possible to accurately refill the liquid container regardless of the amount of liquid remaining in the liquid container without requiring any complex control procedure and complex device. Because only the liquid outlet port is used for drawing out liquid from and filling liquid into the liquid container in the liquid refilling operation, any possible degradation of the performance of the liquid container due to the provision of a liquid flow path not directed to the liquid outlet port is effectively avoided. Additionally, the operator is not required to have a specific skill for the liquid refilling operation nor occupied by the operation for a long period of time.